Gear pump having means to maintain center to center gear alignment



Aug. 11, 1959 J. A. WOTRING ET AL 2,898,863

GEAR PUMP HAVING MEANS TO MAINTAIN CENTER TO CENTER GEAR ALIGNMENT- 2 Sheets-Sheet 1 Filed Feb. 6, 1956 an I m m m o q- M U 5 Rfi 3 e 5 Q I no a N E: Q m

, 5 g E] E INVENTORS TORNEYS g- 1 1959 J. A. WOTRING ET AL 2,898,863

\ GEAR PUMP HAVING MEANS TO MAINTAINCENTER TO CENTER GEAR ALIGNMENT I Filed Feb. e, 1956 Y 2 Sheets-Sheet 2 INVENTORS do/m/ x7. Worm/v0 By dob Iv G MAM/LAND ATTORNEYS United States Patent GEAR PUlVlP HAVING MEANS T MAINTAIN CENTER T0 CENTER GEAR ALIGNMENT John A. Wotring, Painesville, and John G. Mainland,

Cleveland, Ohio, assignors t'o Thompson Ramo Wooldridge Inc., a corporation 'of Ohio Application February 6, 1956, Serial No. 563,478

6 Claims. (Cl. 103- 126) This invention relates generally to gear pumps and more particularly relates to an improved gear pump having means to maintain center to center gear alignment.

In an operating gear pump, the actual running center to center distance of the gears tends to be reduced because the hydraulic pressures developed by the pump forces the gear journals against the loaded side of the bearing bores and forces the bearings against the casing or housing of the pump in which the bearings are mounted. These two movements are additive and in a direction to force the centers of the gears closer together. The resulting change in operating center to center distance may be suflicient to cause tooth interference.

According to the principles of the present invention, the operating phenomenon described is neutralized or compensated for by providing bearing surfaces in the bearings which are offset from true center a suflicient amount that in operating position under loadithe center to center distance of the gears is equal to the nominal center to center distance, thereby avoiding tooth interference.

It is an object of the present invention, therefore, to provide an improved gear pump.

Another object of the present invention is to provide means for maintaining center to center gear alignment in a pump having rotatable fluid displacement means.

Yet another object of the present invention is to provide means for maintaining center to center gear alignment in a pressure-loaded gear pump.

Yet another object of the present invention is to provide a gear pump in which tooth interference is minimized.

A further object of the present invention is to provide a gear pump wherein center to center shifting under load is compensated.

Many other features, advantages and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings in which a preferred structural embodiment of a pressure-loaded gear pump incorporating the principles of the present invention is shown by way of illustrative example.

On the drawings:

Figure 1 is a cross-sectional view of a pressure-loaded gear pump provided in accordance with the principles of the present invention;

Figure 2 is a somewhat schematic view illustrating in exaggerated form the shifting which occurs in a gear pump because of the hydraulic pressures developed by the pump; and

Figure 3 is a somewhat schematic view illustrating in exaggerated form how center to'center gear alignment is maintained in accordance with the principles of the present invention.

As shown on the drawings:

The exemplary pump used to illustrate the principles of the present invention is indicated in Figure 1 generally by the reference numeral and comprises a unitary pump casing 11 housing a plurality of gear pump units indicated by the reference characters A, B and C, respectively, as well as a centrifugal pumping unit indicated by the reference character D.

The casing 11 has an inlet 12 and an outlet 13 formed therein. Fluid drawn from the inlet by a centrifugal impeller .14 is initially pressurized and discharged into a volute pumping chamber 16 whereupon the fluid is supplied to the inlet sides of the respective gear pumping units A, B and C. The gear pumping units A, B and C being in series with the centrifugal impeller 14 additionally pressurized the fluid and discharge the same through the pump outlet 13 for transmission to a point of utilization.

Each of the gear pump units A, B and C is substantially identical and, accordingly, similar reference numerals will be employed wherever possible, a detailed description of only one of the pump units being suflicient for purposes of the present disclosure.

Each pumping unit includes a driver gear 17 and a driven gear 18 particularly characterized by the provision of a plurality of peripheral gear teeth indicated on the driver gear 19 and indicated on the driven gear at 20. The gear teeth 19 and 20 intermesh and upon rotation of the gears 17 and 18 operate to carry fluid from a gear pump inlet portion 21 (Figures 2 and 3) to a gear pump outlet portion 22.

The driver gear 17 has a gear shaft extension 23 extending from one side of the gear hub and a gear shaft extension 24 extending from the other side thereof. In like manner, the driven gear 18 has a first gear shaft extension 26 and a second gear shaft extension 27.

The gear shaft extensions 23 and 26 are journaled in fixed bearing bushings identified by the reference numeral 28.

Each of the fixed bushings 28 includes a tubularbody portion as well as a radially extending flange 29 providing a sealing surface for engaging and sealing against an adjoining side face of a corresponding gear 17 or 18. The tubular body portion of each bushing 28 is particularly characterized by the formation therein of a bore providing an annular bearing surface 30 for journaling a corresponding gear shaft extension 23 or 26 of the respective driver gear 17 or driven gear 18.

On the opposite side of each gear 17 or 18, there is provided a movable pressure-loaded bearing end plate means which takes the form of a bushing member 31 for each respective gear having a tubular body portion and a radially extending flange 32 providing a sealing face for engaging an adjoining side face of a corresponding gear 17 or 18 as well as a motive surface 33 which together with means including a portion of the casing or housing 11 forms a pressure control chamber 34. Fluid at pressure generated by the pump is vented into the pressure control chamber 34 and acts upon the motive surface 33 to pressure-load the movable bushing 31 into sealing engagement with the corresponding gear 17 or 18.

The bushing 31 is particularly characterized by the formation therein of a bore providing an annular bearing surface 36 for journalling a corresponding gear shaft extension 24 or 27 of the respective gears 17 or 18.

All of the pumping units are driven in common from a single driving member indicated at 37. The driving member is retained in the casing 11 by a cover member 38 and the usual means are provided as is indicated generally by the reference numeral 39. The driver member 37 has a collar portion 40 splined to the gear shaft extension 24 of the driver gear 17. There is also provided a quill shaft 41 which is splined as at 42 to the driver member 37. The quill shaft 41 is, in turn, splined as at 43 to the driver gears of the pumping units A and B. A gear train including a gear member 44 and a gear member 46 interconnects the centrifugal impeller 14 and the gear shaft extension on the gear unit A to drive the centrifugal impeller at a correspondingly higher speed than the driver gears of the gear pump units.

In an operating gear pump, the actual running center to center distance of the gears is usually less than the nominal center to center distance. This operating phenomenon is illustrated in Figure 2 wherein the nominal center of the driver gear 17 is indicated at 50 and the nominal center of the driven gear 18 is indicated at 51. Thus, the nominal center to center distance is indicated by the reference numeral 52 directed to the dimension arrow drawn between the two centers. The actual running center of the driver gear 17 is indicated at 53 and the actual running center of the driven gear 18 is indicated at 54. The actual running center to center distance is indicated at 56 and it will be noted that in the exaggerated form of Figure 2 the actual running center to center distance 56 is considerably less than the nominal center to center distance 52. This difference in center to center distances results because the hydraulic pressure developed by the pump forces the gear journals or, in other words, the gear shaft extensions 23, 24, 26, 27 against the loaded side of the bearing bores or bearing surfaces 30, 36. Moreover, the bearings 28 and 31 are forced against the adjoining portions of the casing 11. These two movements are additive and in a direction toforce the centers of the gears 17 and 18 together. In actual practice, this change in operating center to center distance may only amount to several thousandths of an inch, however, such shifting may be sufficient to cause serious problems of tooth interference with respect to the meshing gear teeth 19 and 20.

In accordance with the present invention, the operating phenomena effected by the hydraulic pressure load is neutralized or compensated by machining the bearing surfaces 30 and 36 in offset relation relative to the true center of the bearings 28 and 31 so that in operating position under hydraulic load, the center to center distance of the gears 17 and 18 will be equal to the nominal distance and tooth interference will be avoided or substantially minimized.

The offset machining arrangement is illustrated in Figure 3. Thus, the center of the bearing surfaces 30 and 36 for the driver gear 17 are shifted to a point indicated at 60 and the centers for the bearing surfaces 30 and 36 for the driven gear 18 are shifted to the point 61. The initial center to center distance of the centers 60 and 61 is indicated by the reference numeral 62. In operation, the reduction in center to center distance will again occur, however, the actual running center to center distance will then correspond or coincide with the nominal or true center to center distance 52. Tooth interference will thus be avoided and the pump can be operated at higher speeds with increased capacity.

Although various minor structural modifications might be suggested by those versed in the art, it should be understood that We wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of our contributron to the art.

We claim are our invention:

1 The method of operating a gear-type fluid pump which includes the steps of rotatably driving a pair of gears having intermeshing teeth about their respective centers of rotation at such a speed that the fluidpressure developed thereby acts from the discharge side of the P p In a Converging direction towards the suction side of the pump and forces the gear journals against the loaded side of the bearing bores and the bearings-against the housings to reduce appreciably the actual running center to center distance of the gears OVQI the nominal center to center distance, and shifting the true centers of i said gears outwardly opposite the loaded side of the bear ing bores to offset the actual running center to center distance back to nominal center to center distance, thereby avoiding tooth interference during operation.

2. In a gear-type fiuidpump having an inlet and an outlet, a pair of gears having interrneshing teeth, journal means for each, of said gears, beating means rotatably supporting said journal means, and driving means to rotate said gears on their respective centers of rotation, said bearing means having their centers offset from true center a suflicient distance divergingly outwardly towards the discharge side of the pump and opposite the loaded side of the bearing means so that reduction in center to center distance by converging movement inwardly toward the inlet side of the pump resulting when fluid pressure developed by said pump forces the gear journals against the loaded side of the hearings will be compensated during operation of the gears.

3. In a pump, a casing having an inlet and an outlet, rotary fluid-displacement means in said casing for moving fluid from the inlet to the outlet, bearing means having annular bearing surfaces for journaling said rotary fluiddisplacement means in said casing, said rotary fluid-displacement means forcing the journals thereof against the loaded side of said bearing means and forcing the bearing means against the casing to appreciably shift the actual center of rotation of the rotary fluid-displacement means convergingly inwardly from the nominal center of rotation towards the inlet side of the pump, said bearing means having the axes of said annular bearing surfaces offset from true center divergingly outwardly towards the outlet side of the pump so that in the operating position under hydraulic load the actual center of rotation of said rotary fluid displacement means will coincide with the true center of rotation.

4. In a gear pump, a casing having an inlet and an outlet and a pumping cavity, a pair of rotary gears in said cavity having intermeshing teeth and moving fluid from said inlet to said outlet, bearing means in said casing having annular bearing surfaces for journaling said gears, the actual. running center to center distance of said gears being reduced appreciably by the pressure forces generated by the pump forcing the gear journals convergingly inwardly towards the inlet side of the pump against the loaded side of the bearing surfaces and the bearing means being forced against said casing, said bearing means having the bearing surfaces offset relative to true center of said bearing means divergingly outwardly towards the outlet side of the pump so that in loaded operating condition, the center to center distance of said gears will be equal to the nominal center to center distance, thereby eliminating tooth interference.

5. In a pressure-loaded gear pump, a casing having an inlet and an outlet and a pumping cavity, a pair of rotary gears in said cavity having intermeshing gear teeth and moving fluid from said inlet to said outlet, each of said gears having oppositely extending gear shaft extensions providing journal means for said gears, fixed bushings in said casing on one side of said gears having annular bearing surfaces for journaling corresponding gear shaft extensions of said gears, and movable bushings on the other side of said gears having annular bean'ngsurfaces for journaling corresponding gear shaft extensions on said other side-of said gears, the actual running center to center distance of said gears being reduced appreciably by the pressure forces generated by the pump forcing the gear shaft extensions convergingly inwardly towards the inlet side of the pump and against the loaded side of the bearing surfaces of said fixed bushings and said movable bushings and said fixed bushings and' said movable bushings being forced against said casing, said fixed bushings and said movable bushings having the bearing surfaces thereof offset relative to the true center of said bushings U divergingly outwardly towards the outlet side of the pump to that in loaded operating condition, the center to center distance of said gears will be equal to the nominal center to center distance, thereby eliminating tooth interference between said intermeshing gear teeth.

6. The method of constructing a gear-type fluid pump which includes the steps of ofisetting the bearing surfaces journaling the rotary intermeshing gears divergingly outwardly towards the outlet side of the pump and relative to the true center of the bearing means a sulficient distance outwardly opposite the loaded side of the bearing surfaces that in loaded operating condition the center to center distance of the gears will be equal to the nominal center to center distance, thereby eliminating tooth interference.

References Cited in the file of this patent UNITED STATES PATENTS 1,673,259 Meston et a1. June 12, 1928 1,909,418 Norwood May 16, 1933 1,937,367 Vickers Nov. 28, 1933 2,212,994 Vrolix Aug. 27, 1940 2,310,078 Herman Feb. 2, 1943 2,319,374 Ungar May 18, 1943 2,338,065 Ungar Dec. 28, 1943 

